1. Field of the Invention
The present invention relates to a disk array device and a method of changing the configuration of the disk array device.
2. Description of the Related Art
A disk array device is a device where, for example, plural disk drives are disposed in an array and constructed on the basis of RAID (Redundant Array of Independent Inexpensive Disks) A logical volume that is a logical storage region is formed on a physical storage region that each disk drive has. A LUN (Logical Unit Number) is pre-corresponded to this logical volume. A host computer specifies the LUN, whereby the host computer issues a write command or a read command of a predetermined format with respect to the disk array device. Thus, the host computer can conduct reading and writing of desired data with respect to the disk array device.
As shown in FIG. 14, in the prior art (JP-A-7-20994), plural disk drives 510 are respectively connected to plural disk adapters (DKA) 500. Each disk drive 510 includes plural ports, and these plural ports are respectively connected to the DKA 500 via separate paths. An A port of each disk drive 510 is connected to the DKA 500 via connection boards 520A, and a B port of each disk drive 510 is connected to the DKA 500 via connection boards 520B. Thus, even if trouble arises in the path of either the A port or the B port, the disk drives 510 can be accessed via the other path serving as an alternate path. In the example shown in FIG. 14, RAID groups according to, for example, RAID 5 are configured by the plural disk drives 510 connected to respectively different DKA 500. Thus, even if trouble arises in any one of the disk drives 510 belonging to the same RAID group, data can be recovered on the basis of data stored in the other disk drives 510 belonging to the same RAID group.
As other prior art, the disk array device shown in FIG. 15 is conceivable. In this prior art, disk control units 601 and 602 and disk drives 610 are respectively connected via two connection boards 611 and 612. Each disk drive 610 is respectively disposed with an A port and a B port. The A-side disk control unit 601 shown at the left side of FIG. 15 is respectively connected to the A ports of the plural disk drives 610 via the A-side connection board 611. The B-side disk control unit 602 shown at the right side of FIG. 15 is respectively connected to the B ports of the plural disk drives 610 via the B-side connection board 612.
In recent years, there has been a demand for disk array devices with larger capacity and higher performance. The more the number of disk drives 510 connected to the DKA 500 increases, as in the prior art shown in FIG. 14, the more the processing time required for protocol conversion of interface units increases and data transfer speed also drops. Thus, when the connection number of the disk drives 510 is simply increased, the writing speed and the reading speed from the standpoint of the host computers using the disk array device end up dropping.
A case will be considered where, as shown in FIG. 14, trouble has respectively arisen at two places: sites F1 and F2. When either the connection board 520A or the connection board 520B is replaced in order to recover the trouble, the alternate path of the disk drives 510 connected to the trouble sites F1 and F2 is lost.
That is, in a case where, for example, the connection board 520A is first replaced, the disk drives 510 connected to the trouble site F2 can no longer be accessed from either the A ports or the B ports. This is because the path of the A ports is lost at the point in time when the connection board 520A is removed and the path of the B ports is unusable due to the trouble site F2. In a case where the connection board 520B is first replaced, the alternate path of the disk drives 510 connected to the trouble site F1 is lost. That is, the path of the A ports of the disk drives 510 is unusable due to the trouble site F1 and the path of the B ports is lost at the point in time when the connection board 520B is removed.
It is possible to access the disk drives 510 that are unrelated to the trouble sites F1 and F2. Thus, in a case where trouble has arisen at both of the trouble sites F1 and F2, data that is to be written to the disk drives 510 that have become inaccessible is recovered on the basis of the storage content of other disk drives 510 within the same RAID group after the connection boards 520A and 520B have been respectively replaced with normal connection boards. This data restoration processing (data recovery processing) must be completed before new trouble arises in the disk drives 510 related to the data recovery. This is because it becomes impossible to conduct data recovery in a case where new trouble has arisen prior to the completion of the data recovery processing. In a RAID 5, data can be recovered on the basis of the storage content of the remaining disk drives, even if one of the disk drives within the same RAID group is inaccessible. However, in a RAID 5, data cannot be recovered in a case where plural disk drives have become inaccessible in the same RAID group.
In this manner, in a case where trouble has respectively arisen at the plural trouble sites F1 and F2, it is necessary to conclude data recovery processing before new trouble arises. However, because there is a trend for the number of disk drives 510 connected to the DKA 500 to increase, there is a trend for the period required for data recovery to increase. Also, it is necessary to prevent as much as possible new trouble from arising in other disk drives 510 until the data recovery processing is completed. However, because there has been a demand in recent years for higher density packaging, higher data transfer speed and higher drive access speed, it is not at present simple to significantly lower the rate of occurrence of trouble in the connection boards 520A and 520B and the disk drives 510.
Additionally, in the prior art shown in FIG. 15, the A-side connection board 611 handles the connection to the A ports of the plural disk drive groups and the B-side connection board 612 handles the connection to the B ports of the plural disk drive groups. Thus, in a case where trouble has arisen in one of the connection boards and that connection board is replaced, the plural disk drive groups are affected when the connection board in which the trouble has arisen is removed. Thus, in the prior art shown in FIG. 15, there is the potential for the problems described in connection with FIG. 14 to arise and for the range of influence to increase.